The present invention relates to an area of creating monolithic and hybrid electronic devices having high component packing densities and increased density of interconnections, more particularly, to construction of double-sided electronic devices.
A known construction of stackable flex packaging of chips is disclosed by IBM (Technical Disclosure Bulletin, vol.38, #06 June 1995).
Semiconductor chips are connected, forming a linear array, and are mounted on the both sides of a flexible tape. In addition, flexible wiring may be folded to form a stack. Thermally conductive tape or potting compound may be used to hold the stack of the chips and leads may be brought out of the stack for connection in a next level. Wider tape having several rows of chips similarly disposed may be used for larger chip packages.
A construction of dynamic RAM modules is also taught by a data sheet of Taiyo Yuden Co, Ltd, 1993. Microcircuits having J-leads and "gull wing" leads are mounted on the both sides of a printed circuit board (PCB), having external leads. In this case a thickness of the assembly is 8.89 and 6.5 mm.
In both cases an effort is made to raise the packing density by disposal of electronic components on both sides of a commutation board. But using packaged components and disposing them on both sides of the board make this method of low effectiveness because of the large thickness of the packages. Besides, a process of apparatus automated assembling and repair becomes more complicated because of a necessity of providing common assembly heating and maintaining its integrity.
A known construction of a double-sided electronic cell is described in the book "Design and Calculation of Large Scale Integration Hybrid IC, Microassemblies and Apparatus Based on Them", editor B. F. Visotski, Moscow, Radio and Comm., 1981, p. 126, FIG. 3.11.
A construction of the cell is described having several unpackaged microassemblies, disposed on opposite sides of a printed circuit commutation insert. This method provides a packing density raised by 2 times and a specific power dissipation increased by 1.5-2 times.
A similar construction of a functional group, being a part of a fourth generation apparatus and comprising unpackaged IC, is described in a book by A. P. Nenashev and L. A. Koledov "Fundamentals of Micro-Electronic Apparatus Design", Moscow, Radio and Comm., 1981, p. 261, FIG. 7.10.
The common shortcomings of these constructions are complexity of apparatus assembly and repair and also increased dimensions because of the arrangements of the unpackaged electronic components on the commutation boards' surfaces.
A known technical solution of a power semiconductor circuit is disclosed in German Patent DE 4238555 A1 HO1L, dated Feb. 3, 1994
An integrated circuit is proposed for power semiconductor equipment, which contains power semiconductor devices and a control chain, implemented in a single semiconductor module. Applications of the module are coils AC driving and bipolar power suppliers; additionally, semiconductor devices are disposed on opposite sides of an insulating substance and connected to each other electrically by a through channel, passing through the substance.
A construction of a microwave assembly is known according to a German Patent DE 3934224 A1 HO1L, 27/13 dated Jan. 10, 1991.
A microwave assembly device with a high frequency circuit is patented, implemented on a top surface of an insulating substrate with active elements and conductors. In accordance with the invention a circuit is provided comprising integral power supply elements and decoupling high frequency elements, which are disposed on opposite sides of the substrate. Elements disposed on the opposite side are connected by through contacts.
An advantage of both these last solutions is provided by the double-sided disposal of active and passive elements on surfaces of insulating bases and their electrical connection by through contacts.
Shortcomings are that they are schematic solutions without constructive elements, which do not allow one to apply the solutions in electronic apparatus, and also they provide a complexity of fabrication and impossibility of repair.
Also known is a technical solution according to an article "The Latest Wafer-Scale Design is a Hybrid" (Electronics, 1986, #11, p.28).
In this construction an IC die is disposed in an aperture made in a silicon wafer and is held in it by a polyimide or epoxy compound. The die's active zone is disposed in this case practically on a plane with connecting conductors. An advantage of this construction is derived from the component's disposal inside a commutation board's body.
Shortcomings are single-sided planar disposal of the IC die operating surfaces and also complexity of heat removal and difficulties connected with a difference in TCLE (Temperature Coefficient of Linear Expansion) of the die and compound materials.
Nonetheless, the technical solution in the article "The Latest Wafer-Scale Design is a Hybrid" is the closest analogue of the present invention.
It is apparent from the above analysis that a main problem in creating modern electronic apparatus is obtaining maximum possible packing density while maintaining or improving other technical/economical characteristics.
It is an object of this invention to provide a newin-principle electronic device using both surfaces of a semiconductor substrate or a microboard's substrate for having components working zones thereon. Additionally it is an object of this invention to provide economy of high cost materials (especially pure monocrystalline silicon, heat conductive ceramics etc.); to simplify layouts between structures and components; and to simplify monolithic and hybrid IC fabrication technology.